This invention relates to an improvement of an apparatus for bump-plating semiconductor wafers in which plating liquid is blown up from down to up against the wafers set horizontally in the respective plating basins.
This type of bump-plating apparatus is advantageously used for applying a bump-plating with gold, silver or the like on one surface of a semiconductor wafer, and enables to omit surplus plating steps and materials relating thereto relative to the previous type of the apparatus in which semiconductor wafers to be plated are held with pins at several positions of the periphery of wafers to be dipped in a plating liquid, because it is not required to coat a coating such as photoresist, wax or the like on a wafer surface not to be plated. These matters are described in the previous U.S. Ser. No. 832,332 now U.S. Pat. No. 4,137,867. However, in this type of bump-plating apparatus, plating liquid blown up against the wafer's surface is contacted with the outer peripheral portion more than with the other portions of wafer, and electric field density applied on the outer peripheral portion becomes comparatively high, which result in a thicker plating layer on the outer peripheral portion than the other portions of wafer. While, as semiconductor wafers are processed into elements of extremely delicate electric members, such variety of thickness of plating layer should cause a variety in quality of electronic products. Thus, uniformity of thickness of plating layer has been much desired.